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Re: [Xen-devel] [PATCH 4/8] xen/arm: Store p2m type in each page of the guest





On 12/05/2013 03:55 PM, Ian Campbell wrote:
On Thu, 2013-12-05 at 15:42 +0000, Julien Grall wrote:
Use the field 'avail' to store the type of the page. This information will be
retrieved in a future patch to change the behaviour when the page is removed.

Also introduce guest_physmap_add_entry to map and set a specific p2m type for
a page.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
---
  xen/arch/arm/p2m.c        |   49 +++++++++++++++++++++++++++++++--------------
  xen/include/asm-arm/p2m.h |   18 +++++++++++++----
  2 files changed, 48 insertions(+), 19 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 8f8b47e..5449a35 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -124,7 +124,8 @@ int p2m_pod_decrease_reservation(struct domain *d,
      return -ENOSYS;
  }

-static lpae_t mfn_to_p2m_entry(unsigned long mfn, unsigned int mattr)
+static lpae_t mfn_to_p2m_entry(unsigned long mfn, unsigned int mattr,
+                               p2m_type_t t)
  {
      paddr_t pa = ((paddr_t) mfn) << PAGE_SHIFT;
      lpae_t e = (lpae_t) {
@@ -132,12 +133,25 @@ static lpae_t mfn_to_p2m_entry(unsigned long mfn, 
unsigned int mattr)
          .p2m.af = 1,
          .p2m.sh = LPAE_SH_OUTER,
          .p2m.read = 1,
-        .p2m.write = 1,
          .p2m.mattr = mattr,
          .p2m.table = 1,
          .p2m.valid = 1,
+        .p2m.avail = t, /* Use avail to store p2m type */

Can we change the name in the struct instead and have a comment "using
avail bits for type" there instead please. We only have 5 types so could
only steal 3 but we may as well take all 4.

A BUILD_BUG_ON to check that the last p2m entry is < 2^4 would be good
too.

I will do both modification for the next version.

--
Julien Grall

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